Republican frontrunner Mitt Romney tore into President Barack Obama on Tuesday as he savored his early "Super Tuesday" victories amid cheering supporters in his home state.

"To the millions of Americans who look around and can only see jobs they can't get and bills they can't pay, I have a message," said Romney, amid deafening chants of "USA, USA" and "We need Mitt."

"You have not failed. You have a president that has failed you, and that's going to change... This president's run out of ideas. He's run out of excuses, and in 2012, we're going to get him out of the White House."

He added: "This campaign is not about a name on the ballot. It's about saving the soul of America."

Romney won Massachusetts by a landslide, and won nominating contests in Vermont and Virginia as well, according to US media projections.

But former Pennsylvania senator Rick Santorum won Tennessee and Oklahoma, and Newt Gingrich scored a victory in his home state of Georgia -- meaning Romney did not deliver a knockout punch.

Results were still pending from the key Rust Belt state of Ohio, as well as from Alaska, Idaho and North Dakota.

"There are three states tonight under our belt and counting," Romney told supporters in a ballroom in the Westin Hotel in Boston, with his wife Ann beaming proudly at his side.

"We will get more before this night is over. We're on our way. Your support really means everything to Ann and me. And I'm not going to let you down. I'm going to get this nomination."